rhythm method of birth control

Comparison of birth control methods

Different types of birth control methods have large differences in effectiveness, actions required of users, and side effects.

Ease of use

Different methods require different actions of users. Barrier methods, spermicides, and coitus interruptus must be used at every act of intercourse. The male condom may not be applied until the man achieves an erection. Barriers such as diaphragms, caps, contraceptive sponge, and female condoms may be placed several hours before intercourse begins (note that when using the female condom the penis must be guided into place when initiating intercourse). The female condom should be removed before arising), the other female barrier methods must be left in place for several hours after sex. Spermicides, depending on the form, may be applied several minutes to an hour before intercourse begins.

Oral contraceptives and periodic abstinence methods require some action every day. Other hormonal methods require less frequent action - weekly for the patch, twice a month for vaginal ring, monthly for combined injectable contraceptive, and every twelve weeks for the injection Depo-Provera.

Implants are good for several years. Intrauterine methods require clinic visits for removal and replacement (if desired) only once every few years (5-10, depending on the device). Sterilization is a one-time, permanent procedure - after the success of surgery is verified, no action is usually required of users.

Side effects

Different forms of birth control have different potential side effects. Not all, or even most, users will experience side effects from a method.

The less effective the method, the greater the risk of the side-effects associated with pregnancy.

Minimal or no other side effects are possible with coitus interruptus, periodic abstinence, and LAM. Some forms of periodic abstinence encourage examination of the cervix; insertion of the fingers into the vagina to perform this examination may cause changes in the vaginal environment. Following the rules for LAM may delay a woman's first post-partum menstruation beyond what would be expected from different breastfeeding practices.

Barrier methods have a risk of allergic reaction. Users sensitive to latex may use barriers made of less allergenic materials - polyurethane condoms, or silicone diaphragms, for example. Barrier methods are also often combined with spermicides, which have possible side effects of genital irritation, vaginal infection, and urinary tract infection.

Sterilization procedures are generally considered to have low risk of side effects, though some persons and organizations disagree.

After IUD insertion, menstrual periods are often heavier, more painful, or both - especially for the first few months after they are inserted.

Because of their systemic nature, hormonal methods have the largest number of possible side effects.

Effectiveness calculation

Failure rates may be calculated by either the Pearl index or a life table method. A "perfect-use" rate is where any rules of the method are rigorously followed, and (if applicable) the method is used at every act of intercourse.

Actual failure rates are higher than perfect-use rates for a variety of reasons:

mistakes on the part of those providing instructions on how to use the method

For instance, someone using oral forms of hormonal birth control might be given incorrect information by a health care provider as to the frequency of intake, or by mistake not take the pill one day, or simply not bother to go to the pharmacy on time to renew the prescription, or the pharmacy might be unwilling to provide enough pills to cover an extended absence.

User dependence

Different methods require different levels of diligence by users. Methods that require a clinic visit less than once per year are said to be non-user dependent. Intrauterine methods, implants and sterilization fall into this category. For methods that are not user dependent, the actual and perfect-use failure rates are very similar.

Many hormonal methods of birth control, and LAM require a moderate level of thoughtfulness. For many hormonal methods, clinic visits must be made every three months to a year to renew the prescription. The pill must be taken every day, the patch must be reapplied weekly, or the ring must be replaced monthly. Injections are required every few months. The rules for LAM must be followed every day. Both LAM and hormonal methods provide a reduced level of protection against pregnancy if they are occasionally used incorrectly (rarely going longer than 4-6 hours between breastfeeds, a late pill or injection, or forgetting to replace a patch or ring on time). The actual failure rates for LAM and hormonal methods are somewhat higher than the perfect-use failure rates.

Higher levels of user commitment are required for other methods. Barrier methods, coitus interruptus, and spermicides must be used at every act of intercourse. They do not provide any protection from pregnancy if they are not used. Periodic abstinence methods require daily tracking of the menstrual cycle. They also do not provide any protection from pregnancy if incorrectly used. The actual failure rates for these methods are much higher than the perfect-use failure rates.

Effectiveness of various methods

The table below color codes the typical-use and perfect-use failure rates, where the failure rate is measured as the expected number of pregnancies per year per 100 women using the method:

Blue

under 1%

lower risk

Green

up to 5%

Yellow

up to 10%

Orange

up to 20%

Red

over 20%

higher risk

Grey

no data

no data available

In User action required column, items that are non-user dependent (require action once/year or less) also have a blue background.

Some methods may be combined for higher effectiveness rates. For example, simultaneously using both the male condom and spermicide (applied separately, not pre-lubricated) is believed to reduce perfect-use pregnancy rates to those seen among implant users.

If a method is known to have been ineffective (such as a condom breaking), emergency contraception may be taken up to 120 hours after sexual intercourse. Emergency contraception should be taken as soon after intercourse as possible, as its efficacy decreases with increasing delay.

Comparison table

This table lists the chance of pregnancy during the first year of use.

The word nulliparous refers to those who have not given birth. The word parous refers to those who have given birth. The pregnancy rate applies until the user reaches six months postpartum, or until menstruation resumes, whichever comes first. If menstruation occurs earlier than six months postpartum, the method is no longer effective. For users for whom menstruation does not occur within the six months: after six months postpartum, the method becomes less effective. In the effectiveness study of Lea's Shield, 84% of participants were parous. The unadjusted pregnancy rate in the six-month study was 8.7% among spermicide users and 12.9% among non-spermicide users. No pregnancies occurred among nulliparous users of the Lea's Shield. Assuming the effectiveness ratio of nulliparous to parous users is the same for the Lea's Shield as for the Prentif cervical cap and the Today contraceptive sponge, the unadjusted six-month pregnancy rate would be 2.2% for spermicide users and 2.9% for those who used the device without spermicide. No formal studies meet the standards of Contraceptive Technology for determining typical effectiveness. The typical effectiveness listed here is from the CDC's National Survey of Family Growth, which grouped symptoms-based methods together with calendar-based methods. See Fertility awareness#Effectiveness. The term "fertility awareness" is sometimes used interchangeably with the term "natural family planning" (NFP), though NFP usually refers to use of periodic abstinence in accordance with Catholic beliefs.

Lea's Shield:Mauck C, Glover LH, Miller E, et al (1996). "Lea's Shield: a study of the safety and efficacy of a new vaginal barrier contraceptive used with and without spermicide". Contraception 53 (6): 329–35.